Multilayer absorbent pad

ABSTRACT

An absorbent pad, useful as a diaper, sanitary napkin, or medical dressing, which comprises two superposed liquid-absorbent layers and a liquid-resistant layer disposed between the absorbent layers. The facing surfaces of the absorbent layers have different areas and the surfaces of the resistant layer facing the absorbent layers each have less area than the absorbent layer facing surface of greater area so that liquid flowing into and through the absorbent layer having the facing surface of lesser area and contacting the resistant layer will flow about the edges of the resistant layer into the absorbent layer having the facing surface of greater area.

United States Patent Inventor Pllll W. Jcspersen 3,073,308 1/1963 Stamberger 128/287 Westport, Conn. 3,121,427 2/1964 Mosier 128/285 X Appl. No. 825,247 3,180,335 4/1965 Duncan etal 128/287 Filed May 16,1969 3,371,667 3/1968 Morse [28/296 X Patented July 2 1971 3,386,442 6/1968 Sabee 128/287 Assignee Georgia-Pacific Corporation FOREIGN PATENTS 1,518,000 2/1968 France 128/284 Primary Examiner-Charles F. Rosenbaum UL-"LAYER ABSOREENT p Attorney-Birch, Swindler, McKie & Beckett 18 Claims, 2 Drawing Figs.

US.C1. An absorbent pad useful as a diaper 128/290 R napkin, or medical dressing, which comprises two superposed lnLCl A611 13/16 liquid-absorbent layers d a liquid-resistant layer disposed Field 0 between the absorbent layers The surfaces of the ab.

1 296 sorbent layers have different areas and the surfaces of the resistant layer facing the absorbent layers each have less area Rehnnm CM than the absorbent layer facing surface of greater area so that UNITED STATES PATENTS liquid flowing into and through the absorbent layer having the 1,643,615 9/1927 Williams 128/290 facing surface of lesser area and contacting the resistant layer l/ 1932 Mather.... 128/290 will flow about the edges of the resistant layer into the absor- 2,929,379 3/1960 Poulsen 128/290 bent layer having the facing surface of greater area.

L /QU/0 .MULTILAYER ABSORBENT PAD BACKGROUND OF THE INVENTION l Field of the Invention This invention relates to an absorbent pad, and more particularly to a multilayer absorbent pad having a relatively high capacity for retaining liquids.

- 2. Description of the Prior Art Absorbent pads are well known; such pads being principally used for absorbing and retaining liquids, and exudates discharged from the body. Thus, absorbent pads have been employed as diapers, sanitary napkins and medical dressings.

Frequently, woven sheets of plant and animal fiber yarns, i.e. cotton cloth, have been used for making absorbent pads. Recently, however, nonwoven sheets of cellulosic and other organic fibers have been used for making such pads. The nonwoven sheets are not only less expensive to manufacture than the woven sheets, but generally are disintegratable in water. Therefore, absorbent pads made of nonwoven sheets are ideally suited for disposal after a single use.

Generally, however, absorbent pads made of nonwoven sheets do not disperse the liquid being absorbed uniformly throughout the pad. The liquid thus penetrates a portion of the pad before all portions of the pad have been wetted. This situation constitutes not only a source of discomfort to the user of the pad but also an inefficient use of the nonwetted portions of the pad.

SUMMARY OF THE INVENTION 7 The absorbent pad of the present invention minimizes the foregoing problem. Generally described, the absorbent pad of the invention comprises; first and second superposed liquidabsorbent layers, the surface of the first layer which faces the second layer having less area than the surface of the second layer which faces the first layer; and a liquid-resistant layer disposed between the absorbent layers, the surfaces of the resistant layer which face the absorbent layers each having less area than said second absorbent layer facing surface, the pad being adapted to be worn with the first absorbent layer adjacent the body of a user so that liquid flowing into and through the first absorbent layer and contacting the resistant layer will flow about the edges of the resistant layer into the second absorbent layer.

The surfaces of the resistant layer which face the absorbent layers preferably each have approximately the same area and dimensions as said first absorbent layer facing surface.

Preferably, the pad also includes a liquid-dispersant layer disposed between the second absorbent and resistant layers, the surfaces of the dispersant layer which face the second absorbent and resistant layers each having approximately the same area and dimensions as said second absorbent layer facing surface so that the dispersant layer will distribute liquid flowing about the edges of the resistant layer across said second absorbent layer facing surface.

With the foregoing in mind, it is an object of the present invention to provide an improved absorbent pad.

It is also an object of the invention to provide a multilayer absorbent pad having a high capacity for retaining liquids.

It is a further object of the invention to provide a multilayer absorbent pad in which substantially all portions of the pad become wetted before liquid penetrates any one portion of the pad.

These and other objects of the invention will become apparent upon'a consideration of the following detailed description of a preferred embodiment thereof given in connection with the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the preferred embodiment of the absorbent pad of the invention; and

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of the absorbent pad of the invention is shown in the drawings, as designated by reference numeral 10. Pad 10 comprises a plurality of superposed layers, preferably all of which are disintegratable in water, and including first and second liquid-absorbent layers 12 and 14. Pad 10 is adapted to be worn with layer 12 adjacent the body of a user. Therefore, to facilitate the description of pad 10, the side of the pad adapted to be worm adjacent the body will be referred to as the inner side and the side of the pad adapted to be worn away from the body will be referred to as the outer side. A similar reference system will be used for describing the relationships between the various layers comprising pad 10.

Layers l2 and 14 comprise nonwoven sheets of liquid-absorbent material, such as cellulosic fibers, and/or organic noncellulosic particles and/or fibers as disclosed in Torr US. Pat. Nos. 3,347,236 and 3,070,095. As described in the aforesaid Torr patents, such organic noncellulosic particles and/or fibers preferably comprise the particles and/or fibers of a substance selected from the group consisting of blood albumin, egg albumin, starches, pectin, algin, karaya, tragacanth and guar gums, natural and synthetic gums of polysaccharide character, chemically modified starches, and chemically modified natural and synthetic gums of polysaccharide character. Similarly to many cellulosic substances, such noncellulosic substances are both liquid-absorbent and harmless to the body in either a dry or wetted state. Layers l2 and 14 are rectangularly shaped and are of substantially the same length. However, layer 12 is narrower than layer 14 so that the outer surface of layer 12 has less area than the inner surface of layer 14, i.e. the surface of layer 12 which faces layer 14 has less area than the surface of layer 14 which faces layer 12. Also, layer 12 is transversely centered on layer 14.

Pad 10 also includes a liquid-resistant layer 16 disposed between absorbent layers 12 and 14. Layer 16 may comprise a fluid-impervious sheet, but preferably comprises an air-pervious, substantially liquid-impervious flexible sheet; the term substantially liquid-impervious meaning penetrable by liquid after continuous exposure thereto for a period greater than several seconds, e.e. l5 minutes. Such sheets may comprise a nonwoven sheet of cellulosic fibers having a liquid-repellant coating thereon, i.e. a coating of latex, size or a foam-applied organic suspension, or a sheet of perforated plastic film. The length and width of layer 16 are less than the length'and width of layer 14 so that the inner and outer surfaces of layer 16 each have less area than the inner surface of layer 14, i.e. the surfaces of layer 16 which face layers 12 and 14 each have less area than the surface of layer 14 which faces layer 12. Preferably, the length and width of layer 16 are approximately the same as the length and width of layer 12 so that the inner and outer surfaces of layer 16 each have approximately the same area as the outer surface of layer 12, i.e. the surfaces of layer 16 which face layers 12 and 14 each have approximately the same area and dimensions as the surface of layer 12 which faces layer 14.

Pad 10 further includes a liquid-dispersant layer 18 disposed between outer absorbent layer 14 ad resistant layer 16. Layer 18 comprises a nonwoven sheet of material having a substantially higher capillarity than the material from which absorbent layers 12 and 14 are comprised, such as a creped sheet of cellulosic fibers. The length and width of layer 18 are approximately the same as the length and width of layer 14 so that the inner and outer surfaces of layer 18 each have approximately the same area as the inner surface of layer 14, Le. the surfaces of layer 18 which face layers 14 and 16 each have approximately the same area and dimensions as the surface of layer 14 which faces layer 12.

Pad 10 additionally includes a cover 20 disposed about absorbent layers 12 and I4 and having an inner portion 22 and an outer portion 24. Cover portions 22 and 24 hold the various layers of pad 10 together in assembled condition.

Outer portion 24 is disposed adjacent the outer surface of outer absorbent layer 14 and has approximately the same length and width as layer 14. Similarly to resistant layer 16, outer portion 24 may comprise a fluid-impervious sheet, but preferably comprises an air-pervious, substantially liquid-im pervious, flexible sheet.

Inner portion 22 is disposed adjacent the inner surface of inner absorbent layer 12 with the edges thereof extending beyond the edges of outer absorbent layer 14 and outer portion 24. The edges of portion 22 are wrapped around the edges of portion 24 and are secured to the outer surface of the latter in any convenient manner, as by adhesive bonding or heat sealing. Inner portion 22 comprises a liquid-pervious, nonwoven sheet of nonwettable material, such as a sheet of rayon fibers.

Pad further includes a second liquid-dispersant layer 26 disposed between inner absorbent layer 12 and inner cover portion 22. Similarly to layer 18, layer 26 comprises a non woven sheet of material having a substantially higher capillarity than the material from which absorbent layers 12 and 14 are comprised, such as a creped sheet of cellulosic fibers. The length and width of layer 26 are approximately the same as the length and width of layer 12 so that the inner and outer surfaces of layer 26 each have approximately the same area as the inner surface of layer 12, ie the surfaces of layer 26 which face layer 12 and cover portion 22 each have approximately the same area and dimensions as the surface of layer 12 which faces portion 22.

As mentioned above, pad 10 is adapted to be worn with absorbent layer 12 adjacent the body of a user. lnner cover portions 22 thus is placed in intimate contact with the body so that liquids or exudates discharged from the body flow into the pad in the direction of arrow 28 (H6. 2). The liquid passes through inner cover portion 22 without being absorbed thereby so that the portion of the pad in intimate contact with the body remains relatively dry to provide maximum comfort. After passing through cover portion 22, the liquid flows into dispersant layer 26 which, due to the relatively high capillarity thereof, not only disperses the liquid across the inner surface of absorbent layer 12 but also accelerates the flow of liquid through portion 22.

The liquid flows into and is retained in layer 12 until such layer becomes saturated. Thereafter, since resistant layer 16 is substantially liquid-impervious, the liquid flows about the edges of layer 16 into dispersant layer 18 as shown by arrows 30 (FIG. 2). Resistant layer 16 thus prevents the liquid from flowing directly into layer 18 and thereby minimizes the possibility that the liquid will penetrate one portion of pad 10 before all portions of the pad have been wetted. Dispersant layer 18, similarly to layer 26, not only disperses the liquid across the inner surface of absorbent layer 14, including the portion thereof adjacent the outer surface of layer 16, but also prevents the liquid which flows about the edges of layer 16 from passing back through cover portion 22. In this fashion the liquid flows into layer 14 until such layer becomes saturated.

The above-described flow pattern of liquids within pad 10 provides maximum comfort to a user by minimizing liquidbody contact, and maximizes efficient use of the material from which the pad is comprised by ensuring that substantially all portions of the pad become wetted before liquid penetrates any one portion of the pad. Also, due to such flow pattern, pad 10 has a relatively high capacity for retaining fluids.

If air-pervious, substantially liquid-impervious, flexible sheets are employed for resistant layer 16 and outer cover portion 24, an additional benefit is obtained. Air circulating through cover portion 24 and to a lesser extent layer 16 will promote evaporation of the liquids retained in pad 10 and thus increase the useful life of the pad.

After a single use, pad 10 preferably is disposed of. Since the various layers of the pad preferably are disintegratable in water, one sanitary and expedient method of disposing of a used pad is to discard the pad into a toilet. After soaking for a few moments the various layers of the pad will disintegrate and can be flushed into the sewer.

As will be apparent pad 10 is ideally suited for use as a disposable diaper, sanitary napkin or medical dressing; the size and shape of the pad being tailored to suit the desired use.

While the foregoing constitutes a detailed description of the preferred embodiment of the invention, it is recognized that various modifications thereof will occur to those skilled in the art.

lclaim:

1. An absorbent pad comprising:

first and second superposed liquid-absorbent layers, the surface of said first absorbent layer facing said second absorbent layer having less area than the surface of said second absorbent layer facing said first absorbent layer; and liquid-resistant layer disposed between said absorbent layers and comprising an air-pervious, substantially liquid-impervious, flexible sheet, the surfaces of said resistant layer facing said absorbent layers each having less area than said second absorbent layer facing surface, said pad being adapted to be worn with said first absorbent layer adjacent the body of a user so that liquid flowing into and through the first absorbent layer and contacting the resistant layer will flow about the edges of the resistant layer into the second absorbent layer.

2. An absorbent pad as defined in claim 1, wherein the surfaces of said resistant layer facing said absorbent layers each have approximately the same area and dimensions as said first absorbent layer facing surface.

3. An absorbent pad as defined in claim 1, wherein said first and second absorbent layers comprise nonwoven sheets of liquid-absorbent material.

4. An absorbent pad as defined in claim 3, wherein said liquid-absorbent material includes particles of an organic noncellulosic substance selected from the group consisting of blood albumin, egg albumin, starches, pectin, algin, karaya, tragacanth and guar gums, natural and synthetic gums of polysaccharide character, chemically modified starches, and chemically modified natural and synthetic gums of a polysaccharide character.

5. An absorbent pad as defined in claim 3, wherein said liquid-absorbent material includes fibers of a cellulosic substance.

6. An absorbent pad as defined in claim 1, wherein said sheet comprises a nonwoven sheet of cellulosic fibers having a liquid-repellant coating thereon.

7. An absorbent pad as defined in claim 1, wherein said sheet comprises a sheet of perforated plastic film.

8. An absorbent pad as defined in claim I, wherein said pad further includes a cover disposed about said first and second absorbent layers.

9. An absorbent pad as defined in claim 8, wherein the por- ,tion of said cover disposed adjacent said first absorbent layer comprises a liquid-pervious, nonwoven sheet of nonwettable material.

10. An absorbent pad as defined in claim 9, wherein said nonwettable material comprises rayon fibers.

11. An absorbent pad comprising:

first and second superposed liquid-absorbent layers, the surface of said first absorbent layer facing said second absorbent layer having less area than the surface of said second absorbent layer facing said first absorbent layer; liquid-resistant layer disposed between said absorbent layers, the surfaces of said resistant layer facing said absorbent layers each having less area than said second absorbent layer facing surface, said pad being adapted to be worn with said first absorbent layer adjacent the body of a user so that liquid flowing into and through the first absorbent layer and contacting the resistant layer will flow about the edges of the resistant layer into the second absorbent layer; and cover disposed about said first and second absorbent layers, the portion of said cover disposed adjacent said second absorbent layer comprising an air-pervious, substantially liquidnimpervious, flexible sheet.

12. An absorbent pad as defined in claim 11, wherein said sheet comprises a nonwoven sheet of cellulosic fibers having a liquid-repellant coating thereon.

13. An absorbent pad as defined in claim 11, wherein said sheet comprises a sheet of perforated plastic film.

14. An absorbent pad comprising:

first and second superposed liquid-absorbent layers, the surface of said first absorbent layer facing said second absorbent layer having less area than the surface of said second absorbent layer facing said first absorbent layer; liquid-resistant layer disposed between said absorbent layers, the surfaces of said resistant layer facing said absorbent layers each having less area than said second absorbent layer facing surface, said pad being adapted to be worn with said first absorbent layer adjacent the body of a user so that liquid flowing into and through the first absorbent layer and contacting the resistant layer will flow about the edges of the resistant layer into the second absorbent layer; cover disposed about said first and second absorbent layers; and a liquid-dispersant layer disposed between said second absorbent and resistant layers, the surfaces of said dispersant layer facing said second absorbent and resistant layers each having approximately the same area and dimensions as said second absorbent layer facing surface so that the dispersant layer will distribute liquid flowing about the edges of the resistant layer across said second absorbent layer facing surface.

15. An absorbent pad as defined in claim l4, wherein said pad further includes a second liquid-dispersant layer disposed between said first absorbent layer and said cover, the surfaces of said second dispersant layer facing said first absorbent layer and said cover having approximately the same area and dimensions as the surface of said first absorbent layer facing said cover so that the second dispersant layer will distribute liquid flowing through said cover across said surface of the first absorbent layer facing the cover.

16. An absorbent pad as defined in claim 15, wherein said first-mentioned and second dispersant layers comprise nonwoven sheets of material having a substantially higher capillarity than the material from which said first and second absorbent layers are comprised.

17. An absorbent pad as defined in claim 16, wherein said material of substantially higher capillarity comprises cellulosic fibers.

18. An absorbent pad as defined in claim 15, wherein said first and second absorbent, resistant, and first-mentioned and second dispersant layers are disintegratable in water. 

2. An absorbent pad as defined in claim 1, wherein the surfaces of said resistant layer facing said absorbent layers each have approximately the same area and dimensions as said first absorbent layer facing surface.
 3. An absorbent pad as defined in claim 1, wherein said first and second absorbent layers comprise nonwoven sheets of liquid-absorbent material.
 4. An absorbent pad as defined in claim 3, wherein said liquid-absorbent material includes particles of an organic noncellulosic substance selected from the group consisting of blood albumin, egg albumin, starches, pectin, algin, karaya, tragacanth and guar gums, natural and synthetic gums of polysaccharide character, chemically modified starches, and chemically modified natural and synthetic gums of a polysaccharide character.
 5. An absorbent pad as defined in claim 3, wherein said liquid-absorbent material includes fibers of a cellulosic substance.
 6. An absorbent pad as defined in claim 1, wherein said sheet comprises a nonwoven sheet of cellulosic fibers having a liquid-repellant coating thereon.
 7. An absorbent pad as defined in claim 1, wherein said sheet comprises a sheet Of perforated plastic film.
 8. An absorbent pad as defined in claim 1, wherein said pad further includes a cover disposed about said first and second absorbent layers.
 9. An absorbent pad as defined in claim 8, wherein the portion of said cover disposed adjacent said first absorbent layer comprises a liquid-pervious, nonwoven sheet of nonwettable material.
 10. An absorbent pad as defined in claim 9, wherein said nonwettable material comprises rayon fibers.
 11. An absorbent pad comprising: first and second superposed liquid-absorbent layers, the surface of said first absorbent layer facing said second absorbent layer having less area than the surface of said second absorbent layer facing said first absorbent layer; a liquid-resistant layer disposed between said absorbent layers, the surfaces of said resistant layer facing said absorbent layers each having less area than said second absorbent layer facing surface, said pad being adapted to be worn with said first absorbent layer adjacent the body of a user so that liquid flowing into and through the first absorbent layer and contacting the resistant layer will flow about the edges of the resistant layer into the second absorbent layer; and a cover disposed about said first and second absorbent layers, the portion of said cover disposed adjacent said second absorbent layer comprising an air-pervious, substantially liquid-impervious, flexible sheet.
 12. An absorbent pad as defined in claim 11, wherein said sheet comprises a nonwoven sheet of cellulosic fibers having a liquid-repellant coating thereon.
 13. An absorbent pad as defined in claim 11, wherein said sheet comprises a sheet of perforated plastic film.
 14. An absorbent pad comprising: first and second superposed liquid-absorbent layers, the surface of said first absorbent layer facing said second absorbent layer having less area than the surface of said second absorbent layer facing said first absorbent layer; a liquid-resistant layer disposed between said absorbent layers, the surfaces of said resistant layer facing said absorbent layers each having less area than said second absorbent layer facing surface, said pad being adapted to be worn with said first absorbent layer adjacent the body of a user so that liquid flowing into and through the first absorbent layer and contacting the resistant layer will flow about the edges of the resistant layer into the second absorbent layer; a cover disposed about said first and second absorbent layers; and a liquid-dispersant layer disposed between said second absorbent and resistant layers, the surfaces of said dispersant layer facing said second absorbent and resistant layers each having approximately the same area and dimensions as said second absorbent layer facing surface so that the dispersant layer will distribute liquid flowing about the edges of the resistant layer across said second absorbent layer facing surface.
 15. An absorbent pad as defined in claim 14, wherein said pad further includes a second liquid-dispersant layer disposed between said first absorbent layer and said cover, the surfaces of said second dispersant layer facing said first absorbent layer and said cover having approximately the same area and dimensions as the surface of said first absorbent layer facing said cover so that the second dispersant layer will distribute liquid flowing through said cover across said surface of the first absorbent layer facing the cover.
 16. An absorbent pad as defined in claim 15, wherein said first-mentioned and second dispersant layers comprise nonwoven sheets of material having a substantially higher capillarity than the material from which said first and second absorbent layers are comprised.
 17. An absorbent pad as defined in claim 16, wherein said material of substantially higher capillarity comprises cellulosic fibers.
 18. An absorbent pad as defined in claim 15, wherein said first and second absorbent, resistant, and first-mentioned and seconD dispersant layers are disintegratable in water. 